# ---
# title: 1013. Partition Array Into Three Parts With Equal Sum
# id: problem1013
# author: Indigo
# date: 2021-01-30
# difficulty: Easy
# categories: Array
# link: <https://leetcode.com/problems/partition-array-into-three-parts-with-equal-sum/description/>
# hidden: true
# ---
# 
# Given an array `A` of integers, return `true` if and only if we can partition
# the array into three **non-empty** parts with equal sums.
# 
# Formally, we can partition the array if we can find indexes `i+1 < j` with
# `(A[0] + A[1] + ... + A[i] == A[i+1] + A[i+2] + ... + A[j-1] == A[j] + A[j-1]
# + ... + A[A.length - 1])`
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: A = [0,2,1,-6,6,-7,9,1,2,0,1]
#     Output: true
#     Explanation: 0 + 2 + 1 = -6 + 6 - 7 + 9 + 1 = 2 + 0 + 1
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: A = [0,2,1,-6,6,7,9,-1,2,0,1]
#     Output: false
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: A = [3,3,6,5,-2,2,5,1,-9,4]
#     Output: true
#     Explanation: 3 + 3 = 6 = 5 - 2 + 2 + 5 + 1 - 9 + 4
#     
# 
# 
# 
# **Constraints:**
# 
#   * `3 <= A.length <= 50000`
#   * `-10^4 <= A[i] <= 10^4`
# 
# 
## @lc code=start
using LeetCode

function can_three_parts_equal_sum(arr::Vector{Int})
    function can_three_parts_equal_sum(arr::AbstractVector{Int}, n::Int)
        targ = sum(arr)
        if targ % n != 0 || length(arr) == 0
            return false
        elseif n == 1
            return true
        end
        targ ÷= n
        acc = 0
        for i in 1:length(arr)
            acc += arr[i]
            targ == acc && return can_three_parts_equal_sum(@view(arr[(i + 1):end]), n - 1)
        end
        return false
    end
    return can_three_parts_equal_sum(arr, 3)
end
## @lc code=end
